1. Field
The present disclosure relates generally to imaging and, in particular, to an imaging system using compressive sampling and millimeter waves.
2. Background
Millimeter wave imaging systems have a number of different applications. For example, millimeter wave imaging systems may be used in aircraft landing systems, weapon detection systems, and other suitable applications.
A millimeter wave imaging system operates at millimeter wavelengths. A millimeter wavelength may be from around one millimeter to around ten millimeters. The frequency of millimeter wavelengths may be from around 30 gigahertz to around 300 gigahertz.
Millimeter wave imaging systems may be passive and active. With an active millimeter wave imaging system, the radiation at these wavelengths may have a reduced attenuation over distances of fog or smoke as compared to other wavelengths, such as visible light. As a result, millimeter wave imaging systems have been used to improve visibility through fog for aircraft as part of aircraft landing systems.
Further, millimeter wave imaging systems also are used in security applications to detect hidden weapons and other potential threats. Millimeter waves at millimeter wavelengths are capable of penetrating clothing and significant thicknesses of materials. These materials include, for example, without limitation, dry wood and wall board.
Currently employed millimeter wave imaging systems use a fixed array of detectors, a mechanically scanned detector, or an array of detectors. The different currently available techniques, however, may have drawbacks in cost and/or performance.
For example, with fixed array detectors, a tradeoff between cost and performance is present. Individual detector diodes may be placed at each pixel or array element. The cost for this type of design may be low or reasonable, but a loss of performance occurs with this type of design. The thermal resolution of the discrete diode causes a loss in thermal resolution.
The performance of this type of array may be increased by adding a low noise amplifier to each array element. This performance increase, however, increases the cost and complexity of construction.
In other techniques, a single detector or an array of detectors is used in which the image is scanned across the detector or array of detectors. Desired performance can be obtained without increasing cost. This type of system, however, has an increase in complexity with respect to the mechanical scanning used. Further, with scanning of the image across a detector or array of detectors, an increase in time occurs to generate an image.
Therefore, it would be advantageous to have a method and apparatus that takes into account at least some of the issues discussed above, as well as possibly other issues.